(1) Field of the Invention
The present invention relates to methods used to fabricate semiconductor devices, and more specifically to a method used to form an opening to, and then to protect, a copper structure, during a procedure used to form a fuse opening.
(2) Description of Prior Art
Fuse, of antifuse elements have been used to allow defective regions, in a body of array devices, to be replaced with adjacent, spare device arrays. This is accomplished by placing a programmable fuse or antifuse element, between the main body of gate arrays, and a region comprised of replacement gate arrays. The fuse or antifuse element can sometimes be comprised of a high resistance material, such as amorphous silicon, resulting in an xe2x80x9coffxe2x80x9d state. The high resistance material, although physically connected to both the main body of gate arrays, and the region of replacement arrays, is not electrically connected due its high resistance. A laser or high voltage pulsing procedure, results in the conversion of the high resistance amorphous silicon layer to a low resistance layer, resulting in the xe2x80x9conxe2x80x9d state, featuring electrical, as well as physical connection to both the main body of gate arrays, and to the region of spare gate arrays.
To reduce processing costs and complexity the fuse opening in dielectric layers, used to expose the region of the fuse structure to be pulsed, is sometimes simultaneously accomplished with an opening procedure used to expose the top surface of a metal pad structure, wherein the metal pad structure is either used to accept a wire bond, or to be used as a pad for a xe2x80x9cflip chipxe2x80x9d attachment to a ceramic module, or package. However the underlying fuse structure is located deeper than the metal pad structure, therefore if simultaneous openings are desired, via dry etching procedures, the metal pad structure will be exposed to additional dry etching procedures used to form a deeper opening for exposure of the fuse structure. The exposed metal pad layer, sometimes comprised of copper, can therefore be damaged when subjected to the additional dry etching needed to complete the fuse opening.
This invention will describe a procedure for simultaneously forming openings to a copper pad structure, and to a fuse structure, in which the fuse opening, formed in a group of dielectric layers, is deeper then the opening to the metal pad structure, which is formed in a thinner group of dielectric layers. This is accomplished via forming a barrier layer, overlying a recessed metal pad structure, offering high etch rate selectivity between the dielectric layers, overlying the fuse structure, and the barrier layer, thus protecting the metal, or copper pad structure, during the remaining fuse opening procedure. Prior art, such as Motsiff et al, in U.S. Pat. No. 5,795,819, describe a procedure for simultaneously forming openings to a wire bond pad, and to a fuse structure. However that prior art forms both openings in the same thickness of insulator, therefore not describing the novel barrier layer, overlying a recessed metal pad structure, needed in the present invention for protection of the metal pad structure during the conclusion of the fuse opening procedure.
It is an object of this invention to simultaneously form an opening to a metal pad structure, in a first group of dielectric layers, and to form a deeper opening to a fuse structure, in a second group of dielectric layers, with the first group of dielectric layers included in the thicker, second group of dielectric layers.
It is another object of this invention to recess the metal pad structure, below the top surface of the dielectric layer in which the metal pad structure is located in.
It is still another object of this invention to form a barrier metal shaper on the top surface of the recessed metal pad structure.
It is still yet another object of this invention to simultaneously form openings to the metal pad structure, and to the fuse structure, via a dry etching procedure which exhibits high etch rate selectivity between the groups of dielectric layers, and the barrier metal shape, located on the recessed metal pad structure.
In accordance with the present invention a method of forming an opening to a metal contact structure, and simultaneously forming a deeper opening to a fuse structure, featuring the use of a barrier metal shape, overlying a recessed metal pad structure, is described. A metal contact structure is formed in a dual damascene opening in a first composite dielectric layer. The metal contact structure is then recessed below the top surface of the first composite dielectric, exposing an underlying metal interconnect structure. A barrier metal layer is deposited, then subjected to a chemical mechanical polishing procedure, resulting in the barrier metal shape residing only on the top surface of the recessed metal contact structure. After deposition of an overlying second composite dielectric layer, photolithographic and reactive ion etching, (RIE), procedures are used to form a first opening in the second composite dielectric layer, exposing the top surface of the barrier metal shape, located on the top surface of the recessed metal contact structure; and to form a second opening in the second composite dielectric layer, and in a top portion of the first composite dielectric layer, exposing a region of insulator layer overlying a fuse structure. The barrier metal shape protected the underlying recessed metal contact structure, during the extended RIE procedure. A second barrier metal layer, and a conductive layer, are next deposited, followed by conventional photolithographic and RIE procedures, creating a bonding pad structure, in a region overlying and contacting, the recessed metal contact structure, structure. The same RIE procedure. unprotected by the photoresist shape used to define the bonding pad structure, results in the formation of spacers on the sides of the fuse opening.